The relatively high rates of bulimia nervosa (BN) in attention-deficit/hyperactivity disorder (ADHD) cohorts suggest a relationship between the two disorders. Interestingly, case studies involving this comorbid population have observed improvements in BN symptoms when given psychostimulants for ADHD. Case studies involving BN patents without this comorbidity have also demonstrated BN symptom improvements upon psychostimulant initiation. Recent studies have also found support for the use of lisdexamfetamine dimesylate, a psychostimulant approved for ADHD, for treating moderate to severe binge eating disorder, an eating disorder akin to BN. Given these findings, there is reason to believe that psychostimulants may also be capable of treating bulimia nervosa. Ultimately, the investigators would like to conduct a large study that examines whether people who are diagnosed with BN will have fewer episodes of binge eating and purging when they are treated with the psychostimulant medication, lisdexamfetamine dimesylate (LDX). However, preliminary data would be helpful prior to undertaking such a large project. To this end, the aim of the current study is to learn more about a) enrolment rates, b) dropout rates, c) the applicability of our eligibility criteria, d) the potential effects of LDX on novel outcome measures for studying decision-making in BN, e) preliminary safety data, and f) estimates of treatment effect. Participants (n = 30) will be instructed to take LDX once daily for two months while undergoing routine testing and monitoring to gather preliminary safety and treatment data. The research will take place at the Nova Scotia Health Authority Eating Disorder Clinic.